For single color or multicolor printing of a recording material (for example a single sheet or a belt-shaped recording material) made of the most varied materials, for example paper or thin plastic or metal films, it is known to generate image-dependent potential images (charge images) on an intermediate image carrier (for example a photoconductor) that correspond to the images to be printed and comprised of regions (image areas) that are to be inked and regions that are not to be inked (non-image areas). The regions of the potential images that are to be inked are made visible via toner with a developer station. The toner image is subsequently transfer-printed onto the recording material.
Developer fluid containing toner and carrier fluid can thereby be used to ink the potential images. The carrier fluid thereby has a specific resistance of greater than 108 Ohm*cm. Possible carrier fluids are silicon oil and hydrocarbons, among other things.
One method for electrophoretic liquid developing (electrographic developing) in digital printing systems is known from WO 2005/013013 A2 (=U.S. Pat. No. 7,463,851 B2) or DE 10 2005 055 156 B3 (=US 2008/0279597), for example. A carrier fluid containing silicone oil, with dye particles (toner) dispersed in it, is thereby used as a developer fluid. This can be learned in more detail from WO2005/013013 A2 or DE 10 2005 055 156 B3.
The feed of the liquid developer to the intermediate image carrier can take place via an applicator roller to which the liquid developer is supplied by what is known as a raster or screen roller at which is arranged a chamber blade. The use of chamber blades for ink supply is known from offset printing (EP 1 097 813 A2). The use of a chamber blade in electrophoretic printing can be learned from WO 2005/013013 A2. One disadvantage of the chamber blades known from these is that the flow of the developer fluid in the chamber blade is not specifically directed. Eddies can therefore occur, and air bubbles can be introduced. In addition to this, the filling of the cups of the raster roller takes place without potential assistance, such that the transfer of the toner particles to the raster roller is limited. The achievable toner application per surface element is thereby limited, and therefore the inking region or the speed of the transfer of the developer fluid onto the raster roller (and therefore the achievable process speed given constant inking).
The design of a raster roller that works together with a chamber blade is known from DE 44 08 615 A1. In order to enlarge the shape of the cups of the raster roller, a voltage is applied to the chamber blade and the raster roller. The raster roller is designed such that the shape of the cups can be varied via an electrical voltage.
According to EP 0 727 720 B1 (=U.S. Pat. No. 6,029,036 A), the cleaning of the residual image from the applicator roller (which residual image remains after the development of the potential images on the applicator roller) takes place via a blade resting on the applicator roller. However, an elastic coating of the applicator roller that is required for the nip formation at the intermediate image carrier is rapidly worn by the blade. In contrast to this, if the contact pressure of the blade is too weak a poor cleaning efficiency is accepted, which leads to memory effects given high print utilization (degree of areal coverage of the print image) since not every point of the applicator roller has the same toner quantity/area after a cycle. The cleaning of the applicator roller can also take place via a cleaning roller with blade (DE 10 2005 055 156 B3).